Liquid crystal panel and fabrication method thereof

ABSTRACT

A liquid crystal panel and method for fabricating the same are provided. A plurality of photo spacers and ball spacers are disposed between a color filter substrate and an array substrate. The device for simultaneously applying photo spacers and ball spacers exhibits the ability to eliminate force impact and overcome problems such as touch mura and sound mura.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a division of U.S. patent application Ser. No.11/392,975, filed Mar. 28, 2006, and entitled “LIQUID CRYSTAL PANEL ANDFABRICATION METHOD THEREOF,” which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the invention

The invention relates to a liquid crystal panel and fabrication methodthereof, and more particularly, to a liquid crystal panel havingimproved optical properties.

2. Background

In the current display technology, liquid crystal panel having theadvantages of small size, low weight, low electricity consumption,full-color display, and potentially taking the place of conventionalcathode ray tube (CRT).

Generally speaking, liquid crystal panel fabrication utilizes ballspacers or photo spacers.

FIG. 1 shows a conventional liquid crystal panel using ball spacers. Thepanel comprises color filter substrate 101 and array substrate 102, withball spacers 170 disposed therebetween, and liquid crystal material 180filled therebetween to adjust the amount of light by rotation of liquidcrystal when applying an electric field.

FIG. 2 shows another conventional liquid crystal panel using photospacers. The panel comprises color filter substrate 201 and arraysubstrate 202, with photo spacers 260 disposed therebetween, and liquidcrystal material 180 filled therebetween.

FIG. 3 is a flowchart of a conventional vacuum injection processinjecting liquid crystal material into a panel through an opening in aseal pattern, applying a pressure difference between the interior andexterior of the panel and capillarity.

As shown in FIG. 3, the fabrication process comprises forming a colorfilter substrate and an array substrate in step 30 a and 30 brespectively, forming an alignment layer on the two substratesrespectively in step 31, rubbing the alignment layer to freely alignsubsequently-formed liquid crystal molecules of a liquid crystalmaterial in step 32, forming a seal pattern with an opening in step 33,scattering ball spacers on the array substrate to maintain a uniformcell gap between the two substrates in step 34, bonding the twosubstrates in step 35, cutting the bonded large substrates into aplurality of small panels in step 36, injecting a liquid crystalmaterial into each panel by vacuum injection method in step 37, sealingthe opening of the panels in step 38, and cleaning the panels in step39.

U.S. Patent No. 20040125319 A1 discloses a liquid crystal devicefabricated by conventional vacuum injection, which eliminates gravitymura.

Only a single type of spacers is normally used to maintain uniform cellgap. However, with increased panel size, possible touch mura or soundmura results if only one type of spacers is used.

Moreover, it is difficult to use vacuum injection in panel fabrications,especially in larger panel fabrications. It can take up to 5 days toinject a liquid crystal material into the cell gap of a 30-inch panel byvacuum injection, and utility rate (60% or less) of liquid crystalmaterial is also low. There is therefore a need in panel fabrication toaddress the short injection time requirement and overcome problems suchas touch mura and sound mura.

SUMMARY

In an embodiment, a liquid crystal panel is provided, comprising a firstsubstrate and a second substrate opposite to the first substrate. A gateline and data line are formed on the first substrate, a switch is formedat an intersection of the gate line and the data line, a color filter isformed on the second substrate, a plurality of ball spacers and photospacers are disposed between the first substrate and the secondsubstrate, and a liquid crystal material is interposed between the firstsubstrate and the second substrate.

A method for fabricating a liquid crystal panel is also provided. Afirst substrate is provided. A second substrate is provided. A pluralityof photo spacers is formed on the first substrate. A plurality of ballspacers is formed on the second substrate. A liquid crystal material isdropped on the first substrate or the second substrate, and the twosubstrates are then combined.

In another method for fabricating a liquid crystal panel, a firstsubstrate is provided. A second substrate is provided. A plurality ofphoto spacers and ball spacers is formed on the first substrate. Aliquid crystal material is dropped on the first substrate or the secondsubstrate, and the two substrates are then combined.

DESCRIPTION OF THE DRAWINGS

The invention can be more fully understood by reading the subsequentdetailed description in conjunction with the examples and referencesmade to the accompanying drawings, wherein:

FIG. 1 shows a conventional liquid crystal panel using only ballspacers.

FIG. 2 shows a conventional liquid crystal panel using only photospacers.

FIG. 3 is a flowchart of a conventional process using vacuum injection.

FIGS. 4 a, 4 b, and 4 e illustrate a portion of the liquid crystal panelaccording to an embodiment of the invention.

FIG. 4 c illustrates a process for scattering ball spacers.

FIG. 4 d illustrates One Drop Fill (ODF) process.

FIG. 5 is a flowchart of fabrication of the liquid crystal panelaccording the invention.

DETAILED DESCRIPTION

FIG. 4 a is a color filter substrate 400 having a first substrate 401,which is substantially transparent, preferably of glass, quartz orplastic. The first substrate 401 comprises black matrices 410, colorfilters 421 (R for red), 422 (G for green), 423 (B for blue), atransparent conductive layer 430, and a first alignment layer 441. Theblack matrices 410 can be of chromium (Cr), resin or other opaquematerial. The three colors of R, G, B can be formed on the firstsubstrate 401 to form the color filters 421, 422, and 423 by well-knownmethods such as dyeing, pigment dispersion, printing, orelectro-deposition. The transparent conductive layer 430 can be of oneor more metal oxide layers, such as indium tin oxide (ITO) layer. Thefirst alignment layer 441 can be of polymer, such as polyimide (PI) toform a thin layer at a thickness between about 500 to 1000 Å bywell-known methods such as gravure. Uniform photo spacers 460 are formedon black matrices 410 at a predetermined distance to support the firstsubstrate 401 and the second substrate 402 to maintain a uniform cellgap 490 (as shown in FIG. 4 e). In an embodiment, the photo spacers 460are disposed apart from each other by one pixel intervals in data lineand gate line directions. The photo spacers 460 can be formed byphotolithography or etching. The photo spacers 460 exhibit the abilityto eliminate force impact by absorbing force from pressure or vibration.Photo spacers 460 can be, but are not limited to, disposed on the colorfilter substrate 400, while photo spacers 460 can also be disposed onthe array substrate 400′(as shown in FIG. 4 b). The cross-section ofphoto spacers 460 can be any shape, such as a quadrilateral, hexagon,octagon, polygon, circle, or any other shape. The photo spacer 460 canbe a cube, cylinder, sphere, quadrilateral column, hexagonal column,octagonal column, or any other polygonal column.

FIG. 4 b shows an array substrate 400′ having a transparent secondsubstrate 402, preferably of glass, quartz or plastic, with a circuitlayer 450 and a second alignment layer 442 formed thereon. Although itis not shown in FIG. 4 b, the circuit layer 450 comprises gate lines,date lines, switches, a passivation layer and a transparent conductivelayer. The second alignment layer 442 can be of the same material as thefirst alignment layer 441.

FIG. 4 c shows a scattering of uniform ball spacers 470 on arraysubstrate 400′ to support the first substrate 401 and the secondsubstrate 402 to maintain a uniform cell gap 490 (as shown in FIG. 4 e)by well-known methods such as dry spray or wet spray. The distributiondensity of ball spacers 470 is at least 160 per cm², preferably 160 to300/cm² or 160 to 250/cm², more preferably 160 to 200/cm². Ball spacers470 can be, but are not limited to, disposed on the array substrate400′, while ball spacers 470 can also be disposed on the color filtersubstrate 400. The cross-section of ball spacers 470 can be any shape,such as a quadrilateral, hexagon, octagon, polygon, circle, or any othershape. The ball spacer 470 can be a cube, cylinder, sphere,quadrilateral column, hexagonal column, octagonal column, or any otherpolygonal column. The ball spacers 470 can be resin, silica, glassfiber, or photosensitive materials. Ball spacers 470 eliminate forceimpact by absorbing force from pressure or vibration. For example, thepressures can be 2 kgf of pressure by hand-touch or by a roller fortesting a panel, and the vibrations can be produced by high-frequencyvibration comprising sound vibration from an amplifier near a panel.

FIG. 4 d shows a One Drop Fill (ODF) process, comprising dropping aliquid crystal material 480 on the color filter substrate 400, and thencombining with array substrate 400′ by sealant material pre-coated onthe color filter substrate 400 or the array substrate 400′ to form apanel. After the combination, liquid crystal material 480 is filled inthe space between the two substrates, as shown in FIG. 4 e. Liquidcrystal material 480 can be, but is not limited to, dropped on the colorfilter substrate 400, while liquid crystal material 480 can also bedropped on the array substrate 400′.

FIG. 4 e shows a liquid crystal panel according to an embodiment of thepresent invention. The panel comprises a transparent first substrate 401and a second substrate 402 opposite the first substrate 401. A circuitlayer 450, comprising gate lines, date lines, switches, a passivationlayer and a transparent conductive layer, is formed on the secondsubstrate 402. Color filters 421, 422, and 423 are formed on the firstsubstrate 401. Ball spacers 470 are formed between the first substrate401 and the second substrate 402. The cross-section of ball spacers 470can be any shape, such as a quadrilateral, hexagon, octagon, polygon,circle, or any other shape. The ball spacer 470 can be a cube, cylinder,sphere, quadrilateral column, hexagonal column, octagonal column, or anyother polygonal column. The distribution density of ball spacers 470 isat least 160 per cm², preferably 160 to 300/cm² or 160 to 250/cm², morepreferably 160 to 200/cm². Ball spacers 470 eliminate force impact byabsorbing force from pressure or vibration. For example, the pressurescan be 2 kgf of pressure by hand-touch or by a roller for testing apanel, and the vibrations can be produced by high-frequency vibrationcomprising sound vibration from an amplifier near a panel. Thecross-section of photo spacers 460 can be any shape, such as aquadrilateral, hexagon, octagon, polygon, circle, or any other shape.The photo spacer 460 can be a cube, cylinder, sphere, quadrilateralcolumn, hexagonal column, octagonal column, or any other polygonalcolumn. Photo spacers 460 can also eliminate force impact as described.Liquid crystal material 480 is filled between the two substrates.

FIG. 5 is a flowchart of fabrication of a liquid crystal panel accordingto the invention. In FIG. 5, the fabrication method comprises formingthe two substrates in step 51, forming the two spacers in step 52,forming liquid crystal material in step 53, and combining the twosubstrates in step 54. The fabrication method comprises forming a colorfilter substrate in step 51 a and forming an array substrate in step 51b respectively, then forming photo spacers on the color filter substrateand forming ball spacers on the array substrate in step 52 a, formingball spacers on the color filter substrate and forming photo spacers onthe array substrate in step 52 b, forming photo spacers and ball spacerson the color filter substrate in step 52 c, or forming photo spacers andball spacers on the array substrate in step 52 d, and dropping liquidcrystal material on the color filter substrate in step 53 a or droppingliquid crystal material on the array substrate in step 53 b, andcombining the two substrates to form a panel in step 54.

The device for simultaneously applying photo spacers and ball spacersexhibits the ability to eliminate force impact and overcome problemssuch as touch mura and sound mura. The term “touch mura” means anon-uniform display problem caused by direct touch such as hand-touch;the term “sound mura” means a non-uniform display problem caused byhigh-frequency vibration such as sound vibration from amplifier near apanel.

Sound mura appears in conventional panels using only photo spacers orball spacers, upon on application of sound vibrations to the panel.However, when rolling the inventive panel 3 times at 2 kgf of pressurefrom panel left to right, no touch mura is observed. When furthervibrating the panel at high-frequency such as 80, 160, and 320 MHz, nosound mura is observed. The cell gap of the inventive panel is about 4.5um, photo spacers are about 18 um*18 um*4.7 um, distribution of photospacers is 1 spacer/pixel, diameter of ball spacers is about 4.6 to 4.8um, and ball spacers is about 160 to 200/cm².

While the invention has been described by way of example and in terms ofpreferred embodiment, it is to be understood that the invention is notlimited thereto. To the contrary, it is intended to cover variousmodifications and similar arrangements (as would be apparent to thoseskilled in the art). Therefore, the scope of the appended claims shouldbe accorded the broadest interpretation to encompass all suchmodifications and similar arrangements.

1. A liquid crystal panel, comprising: a first substrate; a secondsubstrate opposite to the first substrate; a gate line and a data linedisposed on the first substrate; a switch disposed at an intersection ofthe gate line and the data line; a color filter disposed on the secondsubstrate; a plurality of black matrices disposed on the secondsubstrate; a plurality of ball spacers disposed between the firstsubstrate and the second substrate; a plurality of photo spacersdisposed between the first substrate and the second substrate; and aliquid crystal material interposed between the first substrate and thesecond substrate, wherein the photo spacers are disposed to overlap theblack matrices.
 2. The liquid crystal panel of claim 1, wherein the ballspacers are distributed at least 160 per cm².
 3. The liquid crystalpanel of claim 1, wherein the ball spacers are distributed about 160 to300 per cm².
 4. The liquid crystal panel of claim 1, wherein the ballspacers and the photo spacers absorb force resulting from pressure orvibration.
 5. The liquid crystal panel of claim 4, wherein the pressurecomprises a direct hand-touch.
 6. The liquid crystal panel of claim 4,wherein the vibration comprises a high-frequency sound vibrationresulting from an amplifier near the liquid crystal panel.
 7. The liquidcrystal panel of claim 1, wherein the cross section of the ball spacersis polygon or circle.
 8. The liquid crystal panel of claim 1, whereinthe cross section of the photo spacers is polygon or circle.